<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python documentation Index' />
<link rel="first" href="lib.html" title='Python library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="encodings-overview.html" />
<link rel="prev" href="module-codecs.html" />
<link rel="parent" href="module-codecs.html" />
<link rel="next" href="codec-objects.html" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name='aesop' content='information' />
<title>4.8.1 Codec Base Classes </title>
</head>
<body>
<div class="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.8 codecs  "
  href="module-codecs.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="4.8 codecs  "
  href="module-codecs.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="4.8.1.1 codec Objects"
  href="codec-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-codecs.html">4.8 codecs  </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-codecs.html">4.8 codecs  </a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="codec-objects.html">4.8.1.1 Codec Objects</a>
</div>
<hr /></div>
</div>
<!--End of Navigation Panel-->

<h2><a name="SECTION006810000000000000000"></a><a name="codec-base-classes"></a>
<br>
4.8.1 Codec Base Classes 
</h2>

<p>
The <tt class="module">codecs</tt> module defines a set of base classes which define the
interface and can also be used to easily write you own codecs for use
in Python.

<p>
Each codec has to define four interfaces to make it usable as codec in
Python: stateless encoder, stateless decoder, stream reader and stream
writer. The stream reader and writers typically reuse the stateless
encoder/decoder to implement the file protocols.

<p>
The <tt class="class">Codec</tt> class defines the interface for stateless
encoders/decoders.

<p>
To simplify and standardize error handling, the <tt class="method">encode()</tt> and
<tt class="method">decode()</tt> methods may implement different error handling
schemes by providing the <var>errors</var> string argument.  The following
string values are defined and implemented by all standard Python
codecs:

<p>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Value</th>
      <th class="left"  >Meaning</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline"><code>'strict'</code></td>
        <td class="left"  >Raise <tt class="exception">UnicodeError</tt> (or a subclass);
                    this is the default.</td></tr>
    <tr><td class="left"   valign="baseline"><code>'ignore'</code></td>
        <td class="left"  >Ignore the character and continue with the next.</td></tr>
    <tr><td class="left"   valign="baseline"><code>'replace'</code></td>
        <td class="left"  >Replace with a suitable replacement character;
                     Python will use the official U+FFFD REPLACEMENT
                     CHARACTER for the built-in Unicode codecs on
                     decoding and '?' on encoding.</td></tr>
    <tr><td class="left"   valign="baseline"><code>'xmlcharrefreplace'</code></td>
        <td class="left"  >Replace with the appropriate XML
                     character reference (only for encoding).</td></tr>
    <tr><td class="left"   valign="baseline"><code>'backslashreplace'</code></td>
        <td class="left"  >Replace with backslashed escape sequences
                     (only for encoding).</td></tr></tbody>
</table></div>

<p>
The set of allowed values can be extended via <tt class="method">register_error</tt>.

<p>

<p><br /></p><hr class='online-navigation' />
<div class='online-navigation'>
<!--Table of Child-Links-->
<a name="CHILD_LINKS"><strong>Subsections</strong></a>

<ul class="ChildLinks">
<li><a href="codec-objects.html">4.8.1.1 Codec Objects</a>
<li><a href="incremental-encoder-objects.html">4.8.1.2 IncrementalEncoder Objects</a>
<li><a href="incremental-decoder-objects.html">4.8.1.3 IncrementalDecoder Objects</a>
<li><a href="stream-writer-objects.html">4.8.1.4 StreamWriter Objects</a>
<li><a href="stream-reader-objects.html">4.8.1.5 StreamReader Objects</a>
<li><a href="stream-reader-writer.html">4.8.1.6 StreamReaderWriter Objects</a>
<li><a href="stream-recoder-objects.html">4.8.1.7 StreamRecoder Objects</a>
</ul>
<!--End of Table of Child-Links-->
</div>

<div class="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.8 codecs  "
  href="module-codecs.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="4.8 codecs  "
  href="module-codecs.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="4.8.1.1 codec Objects"
  href="codec-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-codecs.html">4.8 codecs  </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-codecs.html">4.8 codecs  </a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="codec-objects.html">4.8.1.1 Codec Objects</a>
</div>
</div>
<hr />
<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
</div>
<!--End of Navigation Panel-->
<address>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</address>
</body>
</html>
